I'm reasonably sure that my problem was that on most boats if you are head to wind under power you just sheet tight and power along for a few minutes and hope the wind shifts.
On this Nonsuch however it appears as if the boom has to be over the quarter and never centered. That means you have to drop the sail if powering head to wind as the rig will bounce too much if the boom is over the quarter and the boom will get dangerously close to the head if sheeted in and the mast is bending in the chop.
At least that is what I believe I learned on that boat.
Otherwise the main was cut wrong.